10
Measuring Food Intake
Una E MacIntyre
Key messages- Measuring the food intake in free-living individuals is a complex
task. - All measurements of food intake are subject to sources of error.
- The dietary assessment method used depends on the purpose of
the study. - The existence of error means that it is always important to be
aware of and, whenever possible, to assess the nature and
magnitude of the error.
© 2009 UE MacIntyre.
- To increase our understanding of the error associated with mea-
surements of food intake it is also necessary to develop and use
physiological and biochemical markers of food intake. - To evaluate food intake data effectively it is important to collect
suffi cient additional data to allow individuals to be identifi ed not
only by age and gender, but also by body mass index, physical
activity, and supplement use.
10.1 Introduction
The purpose of this chapter is to describe the various
ways in which one can determine what people eat. The
task may be to fi nd out about the national food supply,
the usual intake of a group or a household, or the
intake of a given individual over a specifi ed period.
The many reasons for fi nding out about the food
that people eat fall into three broad categories:
1 Public Health: to evaluate the adequacy and safety
of the food that people eat at national or commu-
nity level and to identify the need for or to evaluate
nutrition-based intervention programs.
2 Clinical: to assist with the prevention, diagnosis,
and treatment of diet-related conditions.
3 Research: to study the interrelationships between
food intake and physiological function or disease
conditions under controlled conditions or in fi eld
conditions.
The kind and amount of food intake data required
differ in each situation and may require data at the
national, community, household, or individual level.
Assessment of nutritional status
Nutritional health is maintained by a state of equilib-
rium in which nutrient intake is balanced by nutri-
tional requirements. Malnutrition occurs when net
nutrient intake is less than requirements (undernutri-
tion) or exceeds requirements (overnutrition). Both
under- and overnutrition lead to metabolic changes
which have acute and chronic consequences for
health.
There is no ideal tool to measure a person’s nutri-
tional status accurately. Attempts to predict the infl u-
ence of malnutrition based on single measurements
fail to consider the many interacting factors between
nutrition and disease state. For this reason, it is
necessary to look at several different measurements
in order to assess a person’s nutritional status. This
process is known as the A, B, C, D of nutritional
assessment:● Anthropometry (discussed in detail in Chapter 2)
● Biochemical and hematological variables
● Clinical and physical assessment
● Dietary intake.